Overall survival (OS) analysis from PRIME: Randomized phase III study of panitumumab (pmab) with FOLFOX4 for first-line metastatic colorectal cancer (mCRC).

3620 Background: The primary and final analyses of PRIME demonstrated that pmab + FOLFOX4 significantly improved progression-free survival (PFS) vs FOLFOX4 alone for first-line treatment of patients (pts) with wild-type (WT) KRAS exon 2 mCRC. Methods: Pts were randomized 1:1 to pmab 6.0 mg/kg every 2 weeks + FOLFOX4 or FOLFOX4 alone and had no prior chemotherapy for mCRC, ECOG performance status ≤ 2, and tumor tissue for biomarker testing. The primary endpoint was PFS by central assessment. Secondary endpoints included OS, objective response rate, and safety. KRAS exon 2 tumor status was determined by a blinded central lab prior to the primary analysis. This exploratory analysis of updated survival (>80% OS events) estimated the treatment effect of pmab + FOLFOX4 compared with FOLFOX4 alone on OS by KRAS exon 2 status. Previous analyses in pts with WT KRAS exon 2 tumor status reported OS with an event rate of 54% of pts in the primary analysis and 68% of pts in the final analysis. Results: 1183 pts were randomized and received treatment: 593 pts in the pmab + FOLFOX4 arm and 590 pts in the FOLFOX4 alone arm. The KRAS exon 2 ascertainment rate was 93%, consistent with the primary analysis. 535/656 pts (82%) with WT KRAS exon 2 mCRC had an OS event at the time of this analysis. Results are shown (Table). Conclusions: In this updated analysis, an improvement in OS was observed in pts with WT KRAS exon 2 mCRC treated with pmab + FOLFOX4 vs FOLFOX4 alone (p = 0.03). Median OS was reduced in pts with mutant (MT) KRAS mCRC (p = 0.16) and is consistent with previous analyses. Updated efficacy and safety results will be presented. KRAS testing is critical to select appropriate pts with mCRC for treatment with pmab. Clinical trial information: NCT00364013. [Table: see text]